/
lock.go
97 lines (83 loc) · 1.87 KB
/
lock.go
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package storage
import (
"fmt"
"os"
"path"
"strings"
"time"
"github.com/stregato/mio/core"
)
const LockDir = ".lock"
const LockExpire = 10 * time.Second
func Lock(s Store, dir, lockType string, timeout time.Duration) (release chan bool, err error) {
if timeout == 0 {
return tryLock(s, dir, lockType)
}
ticker := time.NewTicker(500 * time.Millisecond)
defer ticker.Stop()
timer := time.NewTimer(timeout)
defer timer.Stop()
for {
select {
case <-timer.C:
return nil, nil
case <-ticker.C:
release, err = tryLock(s, dir, lockType)
if err != nil {
return nil, err
}
if release != nil {
return release, nil
}
}
}
}
func tryLock(s Store, dir, lockType string) (release chan bool, err error) {
dir = path.Join(dir, LockDir)
ls, err := s.ReadDir(dir, Filter{})
if err != nil && !os.IsNotExist(err) {
return nil, err
}
lockName := fmt.Sprintf("%s-%d.lock", lockType, core.SnowID())
lockPath := path.Join(dir, lockName)
err = s.Write(lockPath, core.NewBytesReader(core.GenerateRandomBytes(8)), nil)
if err != nil {
return nil, err
}
time.Sleep(100 * time.Millisecond)
stat, err := s.Stat(lockPath)
if err != nil {
return nil, err
}
oldest := stat
for _, l := range ls {
if strings.HasPrefix(l.Name(), lockType) {
if l.ModTime().Add(LockExpire).Before(stat.ModTime()) {
s.Delete(l.Name())
continue
}
if l.ModTime().Before(oldest.ModTime()) || (l.ModTime().Equal(oldest.ModTime()) && l.Name() < oldest.Name()) {
oldest = l
}
}
}
if oldest != stat {
s.Delete(lockPath)
return nil, nil
}
release = make(chan bool)
go func() {
ticker := time.NewTicker(500 * time.Millisecond)
defer ticker.Stop()
for {
select {
case <-ticker.C:
s.Write(lockPath, core.NewBytesReader(core.GenerateRandomBytes(8)), nil)
case <-release:
s.Delete(lockPath)
return
}
}
}()
return release, nil
}